CN112912773B

CN112912773B - Imaging lens and imaging device

Info

Publication number: CN112912773B
Application number: CN201980068029.4A
Authority: CN
Inventors: 下津臣一
Original assignee: Fujifilm Corp
Current assignee: Fujifilm Corp
Priority date: 2018-11-06
Filing date: 2019-08-27
Publication date: 2024-03-15
Anticipated expiration: 2039-08-27
Also published as: JP2022000708A; US12111560B2; EP3879314A1; JP7443309B2; EP3879314B1; JP6955307B2; CN112912773A; JPWO2020095513A1; US20210208476A1; EP3879314A4; WO2020095513A1

Abstract

The present invention provides an imaging lens capable of improving light transmittance in a specific wavelength region in a near infrared wavelength region more than an imaging lens having a wide light transmittance region, and an imaging device using the imaging lens. The imaging lens has a plurality of lenses, and by applying a coating to at least a part of the plurality of lenses, in a near infrared light wavelength region, a light transmittance at a wavelength side shorter than a near infrared light peak wavelength region NIR including 1550nm decreases as a wavelength becomes shorter from a short wavelength side of the near infrared light peak wavelength region NIR, and a light transmittance at a wavelength side longer than the near infrared light peak wavelength region NIR decreases as a wavelength becomes longer from a long wavelength side of the near infrared light peak wavelength region NIR.

Description

Imaging lens and imaging device

Technical Field

The technology of the present disclosure relates to an imaging lens and an imaging device.

Background

Imaging devices generally capture images under visible light, but imaging devices used in various applications are also known. For example, there are imaging devices that take an image under light of a wavelength in the near infrared region, such as night vision cameras and range finding cameras.

Further, an imaging device capable of capturing images in two wavelength regions, i.e., visible light and near infrared light, is also known. As an imaging element used in such an imaging device, an imaging element capable of detecting light in a wavelength region from visible light to near infrared light is used. For example, patent document 1 discloses an imaging device using a CMOS (complementary metal oxide semiconductor (Complementary Metal Oxide Semiconductor)) sensor or a CCD (charge coupled device (Charge Coupled Device)) sensor. The imaging device described in patent document 1 is an imaging device capable of imaging even in the near infrared region.

Further, as an imaging element having detection sensitivity in a wider near infrared light region, for example, an InGaAs imaging element capable of detecting light in a wavelength region of 0.5 μm to 1.7 μm, or the like can be exemplified.

Technical literature of the prior art

Patent literature

Patent document 1: japanese patent laid-open No. 2004-103964

Disclosure of Invention

Technical problem to be solved by the invention

The imaging device disclosed in patent document 1 can only perform imaging in the near infrared region of 1.1 μm or less. When imaging is performed in a longer wavelength region, a semiconductor imaging element such as InGaAs is required.

An embodiment of the present disclosure provides an imaging lens capable of improving light transmittance in a specific wavelength region in a near infrared wavelength region more than an imaging lens having a wide light transmittance region, and an imaging apparatus using the imaging lens.

Means for solving the technical problems

The imaging lens according to claim 1 includes a plurality of lenses, and the coating is applied to at least a part of the plurality of lenses, whereby in the near-infrared light wavelength region, the transmittance at the wavelength side shorter than the near-infrared light peak wavelength region including 1550nm (1.55 μm) decreases as the wavelength becomes shorter from the short-wavelength side of the near-infrared light peak wavelength region, and the transmittance at the wavelength side longer than the near-infrared light peak wavelength region decreases as the wavelength becomes longer from the long-wavelength side of the near-infrared light peak wavelength region. Therefore, the imaging lens according to claim 1 can further improve the light transmittance in a specific wavelength region within the near infrared wavelength as compared with an imaging lens having a wide light transmittance region.

In the imaging lens according to claim 2, the transmittance in the near infrared peak wavelength region is 60% or more. According to the imaging lens of claim 2, the light transmittance in the near-infrared peak wavelength region is 60% or more, and therefore the light transmittance in the specific wavelength region in the near-infrared wavelength can be improved more than that in the imaging lens having a wide light transmittance region.

In the imaging lens according to claim 3, by applying the coating layer to at least a part of the plurality of lenses, in the visible light wavelength region, the transmittance at the wavelength side shorter than the visible light peak wavelength region including the range of 500nm to 650nm decreases as the wavelength becomes shorter from the short wavelength side of the visible light peak wavelength region, and the transmittance at the wavelength side longer than the visible light peak wavelength region decreases as the wavelength becomes longer from the long wavelength side of the visible light peak wavelength region. According to the imaging lens of claim 3, the visible light peak wavelength region including the range of 500nm to 650nm is provided, so that the light transmittance in the specific wavelength region in the near infrared wavelength can be improved.

In the imaging lens according to the 4 th aspect, at least one 1 st variable of the size and the number of the ripples representing the light transmittance fluctuation characteristic in the near-infrared light peak wavelength region is smaller than the 2 nd variable corresponding to the size and the number of the ripples representing the light transmittance fluctuation characteristic in the visible light peak wavelength region. According to the imaging lens of claim 4, at least one of the size and the number of the ripples in the near-infrared light peak wavelength region is smaller than the size or the number of the ripples corresponding to the light transmittance in the visible light peak wavelength region, so that the light transmittance in the specific wavelength region in the near-infrared wavelength can be improved.

In the imaging lens according to the 5 th aspect, the transmittance of the wavelength region on the short wavelength side in the blue wavelength region included in the visible light wavelength region is lower than the transmittance of the wavelength region on the long wavelength side in the blue wavelength region. According to the imaging lens of claim 5, the transmittance of the blue wavelength region included in the visible wavelength region in the wavelength region on the short wavelength side is lower than the transmittance of the blue wavelength region in the wavelength region on the long wavelength side, so that the transmittance in the specific wavelength region in the near infrared wavelength can be improved.

In the imaging lens according to claim 6, a wavelength region on the short wavelength side of the blue wavelength region is a wavelength region of 450nm or less. According to the imaging lens of claim 6, the transmittance in the wavelength region of 450nm or less in the blue wavelength region is made lower than the transmittance in the wavelength region longer than 450nm, so that the transmittance in the specific wavelength region in the near infrared wavelength can be improved.

In the imaging lens according to the 7 th aspect, the light transmittance of 400nm to 430nm is 50% or less. According to the imaging lens of claim 7, the light transmittance at 400nm to 430nm is 50% or less, so that the light transmittance in a specific wavelength region in the near infrared wavelength can be improved.

The imaging lens according to the 8 th aspect has a low light transmittance region having a smaller light transmittance than the near infrared light peak wavelength region and the visible light peak wavelength region between the near infrared light peak wavelength region and the visible light peak wavelength region by applying a coating to at least a part of the plurality of lenses. According to the imaging lens of claim 8, the low light transmittance region having smaller light transmittance than the near-infrared light peak wavelength region and the visible light peak wavelength region is provided between the near-infrared light peak wavelength region and the visible light peak wavelength region, so that the light transmittance in the specific wavelength region in the near-infrared wavelength can be improved.

In the imaging lens according to the 9 th aspect, the low light transmittance region is a wavelength region of 900nm to 1100nm, and the light transmittance in the wavelength region is 5% or less. According to the imaging lens of claim 9, the low light transmittance region is a wavelength region of 900nm to 1100nm, and the light transmittance in the wavelength region is 5% or less, so that the light transmittance in a specific wavelength region in the near infrared wavelength can be improved.

In the imaging lens according to claim 10, a transmittance peak of one third wavelength of the fundamental wave generated by interference due to the coating layer exists in the visible light peak wavelength region, out of the fundamental wave having a transmittance peak in the near infrared light peak wavelength region. According to the imaging lens of claim 10, the transmittance peak of one third wavelength of the fundamental wave generated by interference due to the coating layer is present in the visible light peak wavelength region, among the fundamental waves having the transmittance peak in the near-infrared light peak wavelength region, so that the transmittance in the specific wavelength region in the near-infrared wavelength can be improved.

The imaging lens according to claim 11 includes a filter switching unit capable of disposing at least one of a 1 st filter for reducing transmittance of at least a part of visible light and a 2 nd filter for reducing transmittance of at least a part of near infrared light on an optical path. According to the imaging lens of claim 11, the optical filter switching unit is provided, which is capable of disposing at least one of the 1 st optical filter for reducing the transmittance of at least a part of visible light and the 2 nd optical filter for reducing the transmittance of at least a part of near infrared light on the optical path, so that the resolution of the captured image can be improved.

In the imaging lens according to claim 12, the product of the refractive index and the thickness of the 2 nd filter is larger than the product of the refractive index and the thickness of the 1 st filter. According to the imaging lens of claim 12, the product of the refractive index and the thickness of the 2 nd filter is larger than the product of the refractive index and the thickness of the 1 st filter, so that the magnitude of the deviation between the focus position in the visible light and the focus position in the near infrared light can be reduced.

The imaging lens according to the 13 th aspect includes a filter switching unit disposed at a position closer to the imaging side than a lens closest to the imaging side among the plurality of lenses. According to the imaging lens of claim 13, even if the filter switching portion is present between the lens located closest to the imaging side and the imaging element, an effect can be obtained.

The imaging lens according to the 14 th aspect includes a control unit that has focus position information indicating a focus position when the 1 st filter or the 2 nd filter is disposed on the optical path, and performs control to change the position of the focus position adjustment lens when the 1 st filter is disposed on the optical path and when the 2 nd filter is disposed on the optical path, based on the focus position information. According to the imaging lens of claim 14, the focal point can be adjusted in near infrared imaging.

The imaging lens according to the 15 th aspect includes a zoom optical system. According to the imaging lens of claim 15, a long-distance subject can be photographed in an enlarged manner in near infrared light.

An imaging device according to the 16 th aspect includes: an imaging lens according to any one of aspects 1 to 15; and an InGaAs imaging element that picks up an image of the subject through an imaging lens. According to the imaging device of claim 16, compared with the case of using an imaging lens having a wide light transmission region, by increasing the light transmittance in a specific wavelength region in the near infrared wavelength, a captured image with high resolution can be obtained.

Effects of the invention

According to an embodiment of the present disclosure, it is possible to provide an imaging lens capable of improving light transmittance in a specific wavelength region in a near infrared wavelength region more than an imaging lens having a wide light transmission region, and an imaging apparatus using the imaging lens.

Drawings

Fig. 1 is a schematic configuration diagram of an imaging device including an imaging lens according to an embodiment.

Fig. 2 is a schematic view of the filter switching section as seen from the A-A direction of fig. 1.

Fig. 3 is a schematic block configuration diagram of an image forming apparatus according to an embodiment.

Fig. 4 is a schematic configuration diagram of a computer according to the embodiment.

Fig. 5 is a flowchart of the focusing process according to the embodiment.

Fig. 6 is a light transmittance distribution of the imaging lens of embodiment 1.

Fig. 7 is a light transmittance distribution of the imaging lens of embodiment 2.

Fig. 8 is an image obtained by imaging using the imaging lens of example 1.

Fig. 9 is an image obtained by imaging with only near infrared light as a subject using the imaging lens of embodiment 1.

Fig. 10 is an image obtained by capturing images of visible light and near infrared light as objects.

Fig. 11 is a graph showing the particle count of fine particles in the atmosphere.

Fig. 12 is a graph showing the amount of light loss due to absorption and scattering in the lens.

Fig. 13 is a conceptual diagram showing a manner in which a program is installed from a storage medium to an image forming apparatus.

Detailed Description

(embodiment)

An example of an embodiment of the technology of the present disclosure will be described below with reference to the drawings.

First, terms used in the following description will be described. In the following description, "CPU" refers to an abbreviation of "central processing unit (Central Processing Unit)". "ROM" refers to the abbreviation "Read Only Memory". "DVD-ROM" refers to the abbreviation "digital versatile disk-Read Only Memory" (Digital Versatile Disc-Read Only Memory) ". "RAM" refers to short for "random access memory (Random Access Memory)". "I/F" refers to the abbreviation of "Interface". "HDD" refers to the abbreviation "Hard Disk Drive". "EEPROM" refers to the abbreviation "electrically erasable programmable read Only memory (Electrically Erasable Programmable Read Only Memory)". "CMOS" refers to an abbreviation for "complementary metal oxide semiconductor (Complementary Metal Oxide Semiconductor)". "CCD" refers to the abbreviation of "charge coupled device (Charge Coupled Device)". "FPGA" refers to the abbreviation "Field programmable gate array (Field-Programmable Gate Array)". "PLD" refers to the abbreviation "programmable logic device (Programmable Logic Device)". "ASIC" refers to the abbreviation of "application specific integrated circuit (Application Specific Integrated Circuit)" (for application specific integrated circuit). "SSD" refers to the abbreviation "solid state disk (Solid State Drive)". "USB" refers to the abbreviation "universal serial bus (Universal Serial Bus)".

It has been known that, especially when a landscape at a long distance is photographed under near infrared light, an image having higher sharpness than an image photographed under visible light can be obtained. This is because the amount of scattering due to the particles present in the atmosphere is smaller in near infrared light than in visible light. The amount of light passing through the atmosphere increases as the distance increases, and the amount of light traveling straight decreases. Therefore, the longer the distance from the subject to the imaging position is, the lower the resolution of an image (hereinafter, also referred to as "imaged image") obtained by imaging is. The fact that a captured image having higher definition in near infrared light than in visible light can be obtained means that the resolution in near infrared light is reduced to a smaller extent than in visible light.

Light scattering by the particles includes rayleigh scattering and mie scattering. Rayleigh scattering is scattering caused by particles having diameters much smaller than the wavelength of light. Mie scattering is scattering caused by particles having diameters relatively close to the wavelength of light. As an index of scattering, there is a scattering parameter α defined by the following formula (1).

α＝πd/λ (1)

Where pi is the circumference ratio, d is the particle size, and λ is the wavelength of light. The mechanism by which light of wavelength lambda is scattered due to particles of diameter d varies according to the scattering parameter alpha. When alpha is less than 1, rayleigh scattering is obtained. When α≡1, it becomes Mie scattering.

Fig. 11 shows a schematic distribution diagram of the particle count of fine water droplets and fine dust contained in the atmosphere. The horizontal axis of fig. 11 represents the diameter of the fine particles, and the vertical axis represents the number of particles in the atmosphere. As shown in fig. 11, there are peaks of vapor particles mainly between several nm to several tens nm and between hundred nm to several hundred nm in particle diameter. That is, it is known that the steam particles having the diameter in this range exist in a large amount. In the case of light passing through the atmosphere, it is scattered mainly by rayleigh scattering caused by vapor particles having the former diameter, and by mie scattering caused by vapor particles having the latter diameter. As a result, as the imaging distance of the imaging device having the imaging lens becomes longer, the amount of light reaching the imaging lens included in the imaging device decreases. The reduction rate is greater in visible light than in near infrared light. Therefore, an image with high resolution can be obtained when imaging with near-infrared light, as compared with when imaging with visible light.

On the other hand, in an imaging lens for photographing in an imaging deviceThe passing light is also scattered and absorbed due to the components of the lens contained in the imaging lens. As shown in fig. 12, light passing through the lens is rayleigh scattered and infrared absorbed due to silica as a main component of the lens. As shown by the one-dot chain line in the figure, the longer the wavelength is, the smaller the rayleigh scattering becomes. Further, as shown by the two-dot chain line in the figure, the absorption of infrared absorption due to si—o bonding starts from around the wavelength of 1.55 μm, and the longer the wavelength, the greater the absorption becomes. In addition, the strong absorption observed around the wavelength of 1.4 μm in the figure is due to OH of the lens component ^- The absorption peak caused.

As is clear from fig. 12, the amount of decrease (loss) in the amount of light due to scattering and absorption in the lens is the lowest range of plus or minus 0.1 μm around the wavelength of 1.55 μm, out of the total of scattering and absorption indicated by the solid line. That is, the transmittance of light of plus or minus 0.1 μm wavelength centered on the 1.55 μm wavelength becomes highest.

In the case of Rayleigh scattering, the scattering intensity is inversely proportional to the wavelength of the scattered light to the power 4. Based on this, if the rayleigh scattering intensity of light of 1.55 μm wavelength is compared with that of light of 0.553 μm wavelength which is visible light, the scattering intensity of light of 1.55 μm wavelength is about 1 of 72 times the scattering intensity of light of 0.553 μm wavelength.

In the case of Mie scattering, it is described in literature that if the forward scattering amount of Mie scattering of light having a wavelength of 1.55 μm is compared with that of light having a wavelength of 0.77 μm, the scattering amount of light having a wavelength of 1.55 μm is about 1 fraction 191 of that of light having a wavelength of 0.77 μm.

As described above, it is known that, of near infrared light, light having a wavelength of around 1.55 μm is the wavelength most suitable for suppressing scattering and absorption in the atmosphere and by lenses. Based on these considerations, the present inventors have found that, in an imaging device capable of imaging with visible light and near infrared light, setting a region including 1.55 μm as an imaging wavelength region of near infrared light is most suitable for improving the resolution of an imaged image.

Therefore, the transmittance distribution generated by the wavelength of the transmitted light of the imaging lens needs to be designed to have a peak value of transmittance in a region containing 1550 nm. Further, since it is preferable to obtain as high a resolution as possible even in the visible light wavelength region, it is preferable to have a region having as high a transmittance as possible even in the visible light wavelength region. As a result of intensive studies by the present inventors, it was revealed that it is useful to form a region having low transmittance between the visible light wavelength region and the near infrared light wavelength region including 1550nm in order to design such that the transmittance distribution based on the wavelength of the transmitted light of the imaging lens has a peak value of transmittance in the region including 1550nm and also has a region having as high transmittance as possible in the visible light wavelength region.

Also, it has been found that by reducing the transmittance at a specific wavelength in visible light, the transmittance in a wavelength region including 1550nm can be further improved. This structure is particularly advantageous in the case where imaging with high resolution is preferable to imaging with respect to visible light in the near infrared light wavelength region including 1550 nm.

On the other hand, the visible light wavelength region of, for example, 0.4 to 0.7 μm has a different number of bits of wavelength difference from the near infrared light wavelength region of 1550 nm. The larger the wavelength difference, the larger the difference in focal length between visible light and near infrared light becomes. Therefore, if imaging is performed using both visible light and near infrared light, both in-focus light and out-of-focus light coexist. This causes a decrease in resolution of the captured image. Therefore, in the imaging device, when imaging is performed, it is preferable to be able to switch between a configuration in which imaging is performed only with visible light and a configuration in which imaging is performed only with near infrared light.

In addition, the difference between the focus positions of the visible light wavelength and the near infrared light wavelength varies according to the magnitude of the zoom magnification. Therefore, when the imaging performed with visible light as an object and the imaging performed with near infrared light as an object are switched, it becomes difficult to readjust the focus position. This is because, in the related art, in light of a specific wavelength, the change of the zoom magnification is performed in conjunction with the adjustment of the focus position. Therefore, in order to adjust the focal positions of the visible light wavelength and the near infrared light wavelength, it is preferable to use a dedicated focus adjustment system and/or to provide an optical member for changing the optical path length of at least either of the visible light and the near infrared light. Hereinafter, the "zoom magnification" is also simply referred to as "magnification".

Next, an imaging device 1 using the imaging lens 100 according to the embodiment will be described with reference to the drawings. As shown in fig. 1, the imaging device 1 includes an imaging lens 100 and an imaging unit 130. The imaging section 130 includes an imaging element 132. The imaging element 132 converts an optical image of an imaging object imaged by the imaging lens 100 into an electrical signal. The imaging device 1 is, for example, a monitoring camera capable of capturing a long distance. As used herein, "remote" refers to distances of, for example, several kilometers to several tens of kilometers.

The imaging lens 100 is a tele lens having a plurality of lenses. The imaging lens 100 includes an objective lens 10, a focusing lens 12, a zoom lens 14, an aperture stop 30, a filter switching unit 50, and an adjusting lens 16 from the object side toward the imaging side. The object side refers to the side where the imaging object exists, and the imaging side refers to the side where the optical image as the object is imaged, that is, the side where the imaging element 132 exists. The term "imaging lens" as used herein refers to, for example, an optical system for imaging an optical image of an imaging object on the imaging surface 132A of the imaging element 132 through a plurality of lenses. The "imaging lens" may include not only a lens but also an optical element such as an aperture, a filter, a half mirror, and/or a deflecting element.

The objective lens 10 is fixed to a housing 90 that holds each optical element such as a lens, and collects light from an imaging object.

The focus lens 12 is an optical system that adjusts the focus position of the object image. The zoom lens 14 is an optical system that adjusts a zoom magnification. The focus lens 12 and the zoom lens 14 are interlocked with each other by a cam mechanism (not shown) and move back and forth along the optical axis OP of the imaging lens 100. Thereby, the magnification is changed and the focus position is adjusted so that the focus position reaches the imaging surface 132A of the imaging element 132. Further, the optical axis OP is also referred to as an optical path OP. The focus lens 12 and the zoom lens 14 are driven by rotating a zoom cam (not shown) by a zoom lens driving mechanism 20. The zoom lens driving mechanism 20 is controlled by the control section 110 in accordance with an instruction issued by the user to the imaging apparatus 1. The zoom lens 14 is an example of a "zoom optical system" according to the technology of the present disclosure.

The aperture 30 is an optical element that shields unnecessary light such as stray light and narrows the light beam. The filter switching unit 50 is a device for switching to a different filter between imaging in visible light and imaging in near infrared light. In fig. 1, the diaphragm 30 is disposed between the zoom lens 14 and the filter switching unit 50, but the position of the diaphragm 30 is not limited to this, and may be disposed so as to be movable between the focus lens 12 and the zoom lens 14, for example.

As shown in fig. 2, the filter switching unit 50 is a turntable type switching device in which four filters 52, 54, 56, and 58 are arranged on a disk. The switching device rotates a disk by a turntable driving mechanism 22 such as a motor to dispose each filter on the optical path OP. The filter switching unit 50 includes a sensor, not shown, for detecting a filter disposed on the optical path OP. The sensor may be provided at a position other than the filter switching section 50 in the turntable driving mechanism 22. The turntable driving mechanism 22 is controlled by the control section 110 in accordance with an instruction issued by the user to the imaging apparatus 1.

In fig. 1, the filter switching unit 50 is disposed between the zoom lens 14 and the adjustment lens 16, but the position of the filter switching unit 50 is not limited to this. The filter switching unit 50 may be disposed between the object side closer to the objective lens 10 and the imaging side closer to the adjusting lens 16. For example, the filter switching unit 50 may be disposed between the adjustment lens 16 and the imaging element 132.

The imaging device 1 may be configured to be able to separate the housing 90 accommodating the imaging lens 100 from the imaging unit 130. For example, the imaging device 1 may be configured such that the housing 90 is a replaceable lens unit, the imaging unit 130 is a camera unit, and any one of a plurality of types of lens units can be mounted on one camera unit. In this case, the filter switching unit 50 may be disposed in the imaging unit 130, i.e., the camera unit.

The filter 52 is a bandpass filter for reducing the transmittance of at least a part of the near-infrared light in the wavelength region. The light transmittance in the wavelength region of at least a part of the near infrared light means, for example, light transmittance in the near infrared light region of the imaging lens 100 with respect to the light transmitting region. The near infrared region is, for example, a wavelength region of 1100nm or more in the near infrared wavelength region. The light transmission region in the near infrared region is, for example, a near infrared peak wavelength region described later. The filter (bandpass filter) 52 is an example of the 2 nd filter according to the technology of the present disclosure. When imaging is performed under visible light by the imaging device 1, the filter 52 is arranged on the optical path OP.

The filter 54 is a bandpass filter that reduces transmittance in a wavelength region of at least a part of visible light. The wavelength region of at least a part of the visible light refers to a light transmitting region in the visible light region of the imaging lens 100. The visible light range is, for example, a wavelength range of 800nm or less. The light transmission region in the visible light region is, for example, a visible light peak wavelength region described later. The filter (bandpass filter) 54 is an example of the 1 st filter according to the technology of the present disclosure. When imaging is performed under near infrared light, the filter 54 is disposed on the optical path OP.

Filter 56 is a transparent glass plate having a refractive index close to that of the other filters 52, 54 and 58. The filter 56 is an optical path length adjustment filter for keeping the optical path length as constant as possible when the other filters 52, 54, and 58 are not used, as well as when the filters 52, 54, and 58 are used. The filter 58 is an ND (neutral Density) filter for adjusting the light amount.

The ND value, which is the product of the refractive index and the thickness of the filter 52, is greater than the ND value, which is the product of the refractive index and the thickness of the filter 54. This is because the difference between the focal position in the visible light and the focal position in the near infrared light is reduced by reducing the difference between the optical path lengths when the visible light and the near infrared light of the light to be imaged are switched. That is, the filter 52 transmits visible light, but has a shorter focal length in the visible light than in the near infrared light. Therefore, by making the ND value of the filter 52 larger than the ND value of the filter 54 transmitting near infrared light, the optical path length is increased. With this structure, the deviation between the focus position in the visible light and the focus position in the near infrared light can be reduced. The configuration of changing the ND value of the filter 52 and the ND value of the filter 54 is useful when the deviation between the focus position in the visible light and the focus position in the near infrared light cannot be adjusted by the adjustment lens 16 alone, which will be described below.

The adjustment lens 16 is a lens for adjusting the difference between the focal length under visible light and the focal length under near infrared light when the filter 52 and the filter 54 are switched. The focal length of near infrared light having a longer wavelength than visible light is longer than that of visible light. The focus lens 12 and the zoom lens 14 are configured to move in linkage so that the focus position at the time of magnification change in visible light is aligned with the imaging surface 132A of the imaging element 132, and therefore the focus position in near infrared light cannot be adjusted. Therefore, when imaging is performed under near infrared light, that is, when the filter 54 is arranged on the optical path OP, the adjustment lens 16 moves so that the focus position is aligned with the imaging surface 132A according to focus position data described later. The adjustment lens 16 is an example of "focus position adjustment lens" according to the technology of the present disclosure.

The steering lens 16 is driven by a steering lens driving mechanism 24. The control unit 110 controls and adjusts the lens driving mechanism 24 in response to an instruction from the user. Specifically, the control section 110 controls the adjustment lens driving mechanism 24 according to the imaging condition instructed by the user to adjust the position of the adjustment lens 16 to the focus position. Here, the imaging conditions are, for example, selection of visible light or near infrared light and selection of zoom magnification according to an instruction from a user. The focal position of the adjustment lens 16 is a position of the adjustment lens 16 for imaging light in a focused state on the imaging surface 132A of the imaging element 132.

Alternatively, the control unit 110 may adjust the position of the adjustment lens 16 based on the focus position data, similarly to the filter arranged on the optical path OP based on the filter position information from the sensor provided in the filter switching unit 50. For example, if imaging under visible light is instructed to the control unit 110 by the user through the input unit 28 described later, the filter 52 is arranged on the optical path OP by the control unit 110. If the user instructs the control unit 110 to perform imaging in near infrared light through the input unit 28, the filter 54 is disposed on the optical path OP through the control unit 110. The control unit 110 detects the type of the optical filter on the optical path OP by a sensor provided in the optical filter switching unit 50, and adjusts the position of the adjustment lens 16 according to the detected type of the optical filter. In addition, the adjustment lens 16 may also be used to adjust the flange distance when the imaging section 130 is replaced.

As an example, as shown in fig. 3, the imaging device 1 is controlled by the control section 110. The control unit 110 includes a computer 200. As an example, as shown in fig. 4, the computer 200 has a CPU202, a RAM204, and a ROM206 connected to each other by a bus 112. The CPU202 controls the entire imaging apparatus 1. The RAM204 is, for example, a volatile memory that serves as a work area or the like when executing an imaging device control program. The ROM206 is, for example, a nonvolatile memory storing an imaging device control program 210 and focus position data 212 that control the imaging device 1. In the present embodiment, the CPU202 is exemplified, but a plurality of CPUs may be used instead of the CPU202.

The CPU202 reads the imaging device control program 210 from the ROM206, and presents the read imaging device control program 210 to the RAM204. Then, the CPU202 executes the imaging device control program 210 to control the zoom lens driving section 114, the turret driving section 116, and the adjustment lens driving section 118 shown in fig. 3 as an example.

The in-focus position data 212 is data in which the position of the adjustment lens 16 when imaging is performed under visible light and the position of the adjustment lens 16 when imaging is performed under near infrared light are correlated with magnification. As described above, the case where the filter 52 is arranged by the filter switching unit 50 when imaging is performed under visible light is referred to. The case of imaging in near infrared light means that the filter 54 is disposed by the filter switching unit 50. The in-focus position data 212 is stored as position data of the adjustment lens 16 in accordance with magnification in visible light and near infrared light, for example.

The focus position data 212 is an example of "focus position information" related to the technology of the present disclosure.

The zoom lens driving mechanism 20, the turret driving mechanism 22, and the adjustment lens driving mechanism 24 may be any known mechanism.

Although these mechanisms are shown in fig. 1 as being located inside the housing 90, they may be located outside the housing 90.

The imaging element 132 is, for example, an InGaAs imaging element capable of imaging an object with wavelengths of both visible light and near infrared light. The optical image formed by the imaging lens 100 is converted into an electrical signal by the imaging element 132 of the imaging section 130, subjected to various image processing, and then displayed as an image on the image display section 26 described later. And, the image after the image processing may be transmitted to the outside through a wire or wirelessly.

As shown in fig. 3, the control section 110 includes a zoom lens driving section 114, a turret driving section 116, an adjustment lens driving section 118, an output I/F120, an input I/F122, an image processing section 126, and a computer 200. Which are connected by a bus 112. The control unit 110 includes an external I/F not shown.

The zoom lens driving unit 114 is connected to the zoom lens driving mechanism 20. The turntable driving section 116 is connected to the turntable driving mechanism 22. The adjustment lens driving unit 118 is connected to the adjustment lens driving mechanism 24. The output I/F120 is connected to the image display unit 26. Input I/F122 is connected to imaging element 132 and input 28.

The image display section 26 displays an image based on an image signal input through the output I/F120. The input 28 receives an instruction given by a user. The input I/F122 is an interface for receiving an electric signal from the imaging element 132 and an instruction input by a user through an input section, and transmitting the instruction to the computer 200. The external I/F is, for example, an interface for receiving an instruction from a user through wireless communication, and transmitting an image subjected to image processing through wireless communication. The image processing section 126 performs image processing on the image acquired by the imaging element 132.

The zoom lens driving unit 114 adjusts the position of the focus lens 12 and the position of the zoom lens 14 by controlling the zoom lens driving mechanism 20 according to an instruction from the computer 200. The turntable driving unit 116 controls the turntable driving mechanism 22 to switch the filter of the filter switching unit 50 according to an instruction from the control unit 110. The adjustment lens driving unit 118 adjusts the position of the adjustment lens 16 by controlling the adjustment lens driving mechanism 24 in accordance with an instruction from the control unit 110. The output I/F120 is an interface for transmitting the captured image obtained by performing image processing by the image processing section 126 to the image display section 26.

Next, an example of drive control (focusing process) performed by the CPU202 on the filter switching unit 50 and the adjustment lens 16 will be described with reference to fig. 5. Fig. 5 is a flowchart showing an example of the flow of the focusing process executed by the CPU202 according to the imaging device control program 210. The focusing process shown in fig. 5 is a process on the premise that the user instructs a condition for imaging in the visible light or in the near infrared light through the input unit 28, and drives the filter switching unit 50 and the adjustment lens 16 according to the instructed imaging condition.

First, in step S10, the CPU202 determines whether or not the user instructs image capturing under visible light. In step S10, when image capturing under visible light is instructed by the user, the determination is affirmative, and the focusing process proceeds to step S12. In step S10, when the user does not instruct imaging under visible light, the determination is negative, and the focusing process proceeds to step S16.

In step S12, the CPU202 controls the turret driving section 116 to dispose the optical filter 52 on the optical path OP.

In the next step S14, the CPU202 controls the adjustment lens driving section 118 to move the adjustment lens 16 so that the focus position in the visible light is aligned with the imaging surface 132A of the imaging element 132, thereby ending the process.

In step S16, the CPU202 determines whether the user instructs imaging under near infrared light. In step S16, when the user instructs imaging under near infrared light, the determination is affirmative, and the focusing process proceeds to step S18. In step S16, when the user does not instruct imaging under near infrared light, the determination is negative, and the focusing process is ended.

In step S18, the CPU202 controls the turret driving section 116 to dispose the optical filter 54 on the optical path OP.

In the next step S20, the CPU202 moves the adjustment lens 16 so that the focus position in the near infrared light is aligned with the imaging surface 132A of the imaging element 132, and thereafter ends the focusing process.

As described above, the control unit 110 has focus position information indicating a focus position in a case where the filter 54 as an example of the 1 st filter or the filter 52 as an example of the 2 nd filter is arranged on the optical path, and performs control to change the position of the focus position adjustment lens in a case where the filter 54 as an example of the 1 st filter is arranged on the optical path and in a case where the filter 52 as an example of the 2 nd filter is arranged on the optical path based on the focus position information. This allows easy focus adjustment in near infrared imaging.

The above-described focusing process is merely an example. Accordingly, unnecessary steps may be deleted, new steps may be added, or the processing order may be changed within a range not departing from the spirit.

In the present embodiment, an example in which the imaging device control program 210 and the focus position data 212 are stored in the ROM206 of the control unit 110 has been described, but the technology of the present disclosure is not limited to this. For example, at least one of the imaging device control program 210 and the focus position data 212 may also be stored in an HDD, EEPROM, flash memory, or the like connected to the bus 112.

As shown in fig. 13, the imaging device control program 210 may be stored in any portable storage medium 300 such as an SSD, a USB memory, or a DVD-ROM. In this case, the imaging device control program 210 stored in the storage medium 300 is installed in the computer 200 of the control section 110, and the installed imaging device control program 210 is executed by the CPU202 of the control section 110.

The imaging device control program 210 may be stored in a storage unit such as a server device or another computer connected to the control unit 110 of the imaging device 1 via a communication network (not shown), and the imaging device control program 210 may be downloaded according to a request of the imaging device 1. In this case, the downloaded imaging device control program 210 is executed by the CPU202 of the control section 110.

The control unit 110 may be disposed in the housing 90 of the imaging lens 100. Alternatively, the imaging unit 130 may be disposed instead of the housing 90 of the imaging lens 100. When there are a plurality of types of imaging lenses 100, by disposing the control unit 110 storing all control programs for the respective imaging lenses in the imaging unit 130, even when different types of imaging lenses 100 are replaced in accordance with the housing 90, the replaced imaging lenses 100 can be controlled by the control unit 110.

Next, the light transmittance of the imaging lens 100 will be described. Each lens of the imaging lens 100 is coated to have high light transmittance in a specific wavelength region of visible light and near infrared light. The coating is preferably formed by laminating a material, which causes TiO to form a film, in a plurality of layers on the lens surface ₂ ，Ta ₂ O ₅ ，Al ₂ O ₃ ，SiO ₂ ，MgF ₂ Etc. By adjusting the refractive index, thickness, and number of layers of the material forming the thin film, it is possible to increase the light transmittance in a specific wavelength region and decrease the light transmittance in a specific wavelength region. The coating material, the coating thickness, and the number of coating layers for increasing the light transmittance in a specific wavelength region and decreasing the light transmittance in a specific wavelength region can be designed according to computer simulation or the like.

The light transmittance is a ratio of the intensity of light emitted from the lens when light of a certain wavelength is incident on the lens, for example, to the intensity of light incident on the lens, and can be expressed by the following formula.

Transmittance (%) =100× (outgoing light intensity)/(incoming light intensity)

Although shown schematically in fig. 1, the objective lens 10, the focus lens 12, the zoom lens 14, and the adjustment lens 16 are each composed of 1 or more lens groups. The imaging lens 100 is constituted by several to several tens of lenses as a whole. Each lens of the imaging lens 100 is coated so as to have high light transmittance in a specific wavelength region in visible light and near infrared light. The coating may also be applied to only a portion of all lenses. However, it is more preferred that the coating is applied to all lenses.

As described above, in the case where a user photographs a landscape or the like with near infrared light, scattering and absorption of the atmosphere and near infrared light by the lens are minimized around 1550nm, and therefore it is preferable that the imaging lens has as high light transmittance as possible around 1550 nm. Further, since imaging can be performed even in visible light, the imaging lens preferably has high light transmittance in a visible light region as wide as possible.

In order to satisfy the above two conditions, it is preferable that in the near infrared light wavelength region, the near infrared light peak wavelength region including 1550nm has a peak of light transmittance in the near infrared light wavelength region. That is, it is preferable that the transmittance at the wavelength side shorter than the near infrared light peak wavelength region including 1550nm is reduced from the short wavelength side of the near infrared light peak wavelength region as the wavelength becomes shorter, and the transmittance at the wavelength side longer than the near infrared light peak wavelength region is reduced from the long wavelength side of the near infrared light peak wavelength region as the wavelength becomes longer.

Also, it is preferable to have a visible light peak wavelength region including a range of 500nm to 650nm in the visible light wavelength region. That is, it is preferable that the transmittance on the wavelength side shorter than the visible light peak wavelength region including the range of 500nm to 650nm decreases from the short wavelength side of the visible light peak wavelength region as the wavelength becomes shorter, and the transmittance on the wavelength side longer than the visible light peak wavelength region decreases from the long wavelength side of the visible light peak wavelength region as the wavelength becomes longer.

The inventors have found that by applying a coating layer forming a light transmittance peak having the above-described characteristics, an imaging lens having high resolution in both near infrared light and visible light can be manufactured, and particularly an imaging lens having very high resolution in near infrared light can be manufactured.

The "near-infrared peak wavelength region" refers to a wavelength region in which a peak of light transmittance in the near-infrared wavelength region is allowed to exist in design in order to increase the light transmittance around 1550nm as much as possible. As described below, there may be a plurality of peaks of the same or different heights in the near infrared peak wavelength region. The near-infrared light peak wavelength region is, for example, a region having a wavelength of 1450nm to 1650 nm. Preferably, the near infrared peak wavelength region is a region having a wavelength of 1480nm to 1620 nm. More preferably, the near infrared peak wavelength region is a region having a wavelength of 1500nm to 1580 nm. In particular, when the imaging lens 100 is configured as a tele zoom lens capable of observing a long distance, as the light transmittance in the near infrared peak wavelength region decreases, the observation distance decreases, and therefore the light transmittance in the near infrared peak wavelength region becomes important. For example, when the light transmittance around 1550nm is about 90%, a place as long as 30km or more can be observed. Further, when the transmittance is 60% or more in the vicinity of 1550nm, it is expected that an observation distance of about 20km is ensured.

The light transmittance in the near infrared peak wavelength region is preferably 60% or more, more preferably 70% or more, and further preferably 80% or more. The peak value of the light transmittance in the near-infrared light peak wavelength region is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. In particular, the light transmittance at a wavelength of 1550nm is preferably 80% or more, more preferably 85% or more, still more preferably 88% or more, and still more preferably 90% or more.

The "visible light peak wavelength region" is a wavelength region in which the peak value of the light transmittance in the visible light wavelength region is allowed to exist in design in order to increase the light transmittance around 1550nm as much as possible and to ensure a high light transmittance in the visible light wavelength region. As described below, there may be a plurality of peaks of the same or different heights in the visible peak wavelength region. The visible light peak wavelength region is, for example, a region having a wavelength of 450nm to 700 nm. Preferably, the visible light peak wavelength region is a region having a wavelength of 480nm to 680 nm. More preferably, the visible light peak wavelength region is a region having a wavelength of 500nm to 650 nm.

The transmittance in the visible light peak wavelength region is preferably 50% or more, more preferably 60% or more, and further preferably 70% or more. The peak value of the transmittance in the visible light peak wavelength region is preferably 85% or more, more preferably 90% or more, and further preferably 93% or more.

The light transmittance is the light transmittance of the entire plurality of lenses of the imaging lens 100. The light transmittance of the imaging lens 100 as a whole is an integrated value of the light transmittance of each lens. For example, if the light transmittance of each lens is set to X identically and the number of lenses is set to n, the light transmittance X of the imaging lens 100 as a whole is given by x=xn. The light transmittance of each lens is preferably 95% or more, more preferably 98% or more, and still more preferably 99% or more, although also depending on the number of lenses.

For example, in the case of the imaging device 1 for long-distance imaging, the setting of the light transmittance of the imaging lens 100 as a whole is determined in consideration of the distance to the subject imaged by the imaging device 1 under near infrared light and the resolution of the subject image. The resolution can be defined, for example, by the maximum distance at which an object having a predetermined size at a position separated by a certain distance can be recognized in an image obtained by capturing the object by the imaging device 1. The transmittance for obtaining the resolution thus determined is determined by actual measurement or simulation or the like, and the transmittance of each lens is determined according to the total number of lenses. Then, the light transmittance distribution of one lens is determined by the above method, and a coating layer which can obtain the light transmittance distribution is performed. In addition, when the light transmittance is set, it can be determined by evaluation of other resolutions. Further, the light transmittance may be determined from other viewpoints without using resolution.

Examples

Example 1

Fig. 6 shows a distribution of light transmittance of the imaging lens 100 according to embodiment 1. In fig. 6, the horizontal axis represents wavelength, and the vertical axis represents light transmittance of the imaging lens 100. As shown in fig. 6, the distribution of light transmittance of the imaging lens 100 NIR has a 1 st transmittance peak PK1 in a near infrared light peak wavelength region of 1450nm to 1650 nm. That is, the transmittance at the wavelength side shorter than the near infrared peak wavelength region NIR decreases as the wavelength becomes shorter from the transmittance at the short wavelength end (1450 nm) of the near infrared peak wavelength region NIR. The transmittance at the wavelength side longer than the near infrared peak wavelength region NIR decreases as the wavelength increases from the transmittance at the long wavelength end (1650 nm) of the near infrared peak wavelength region NIR.

As can be seen from fig. 6, the transmittance of the 1 st transmittance peak PK1 is about 92% at a wavelength of 1520 nm. And the transmittance in the range of 1490nm to 1560nm is 90% or more.

Also, the distribution of light transmittance of the imaging lens 100 has a 2 nd transmittance peak PK2 in a visible light peak wavelength region VIS of 450nm to 700 nm. That is, the transmittance at the wavelength side shorter than the visible light peak wavelength region VIS decreases from the transmittance at the short wavelength end (450 nm) of the visible light peak wavelength region VIS as the wavelength becomes shorter. The transmittance at the longer wavelength side than the visible light peak wavelength region VIS decreases as the wavelength increases from the long wavelength end (700 nm) of the visible light peak wavelength region VIS.

As can be seen from fig. 6, the transmittance of the 2 nd transmittance peak PK2 is about 96% at a wavelength of 570nm to 580 nm. And a light transmittance in a range of 480nm to 660nm is 90% or more.

Further, the transmittance of the wavelength region on the short wavelength side of the blue wavelength region included in the visible light wavelength region is lower than the transmittance of the wavelength region on the long wavelength side of the blue wavelength region. Specifically, the transmittance in the wavelength region of 450nm or less in the blue wavelength region is smaller than the transmittance in the wavelength region longer than 450 nm. And a light transmittance of 50% or less at a wavelength of 400nm to 430 nm. If the light transmittance at a wavelength of 400nm to 430nm is set to be more than 50%, the light transmittance at a wavelength of 1200nm to 1290nm, which is a wave 3 times the peak of the near infrared band, becomes large. This means that the peak in the near infrared wavelength region becomes broader, and there is a possibility that the transmittance at a wavelength around 1550nm is lowered, or that characteristics such as moire residue are deteriorated.

Further, the imaging lens 100 has a LOW light transmittance region LOW having a light transmittance smaller than the near infrared light peak wavelength region and the visible light peak wavelength region in a range of 900nm to 1100nm in wavelength between the near infrared light peak wavelength region and the visible light peak wavelength region. The light transmittance of the LOW light transmittance region LOW is preferably 5% or less. The LOW light transmittance region LOW is a region that is generated with the formation of a light transmittance peak in the near infrared light region in the near infrared light peak wavelength region NIR, and the formation of a light transmittance peak in the visible light region in the visible light peak wavelength region VIS. However, since the wavelength of the LOW light transmittance region LOW is a wavelength region that does not contribute to imaging both in visible light and near infrared light, the LOW light transmittance of the LOW light transmittance region LOW does not become a problem.

The distribution of light transmittance shown in fig. 6 has one light transmittance peak PK1 in the near infrared light peak wavelength region NIR and one light transmittance peak PK2 in the visible light peak wavelength region VIS. However, the distribution of light transmittance of the present disclosure is not limited thereto. The NIR may also have a plurality of waveform shapes (ripples) caused by the light transmittance peaks in the near infrared peak wavelength region. Further, the VIS may have a ripple in the visible light peak wavelength region. The moire is a shape representing one characteristic of fluctuation of light transmittance. As described above, the number of the transmittance peaks, which are whether or not moire, is not limited as long as the NIR has a transmittance peak in the near infrared peak wavelength region and the VIS has a distribution of the transmittance peak in the visible peak wavelength region.

The 1 st transmittance peak PK1 formed in the near infrared peak wavelength region NIR is preferably as narrow as possible in half-peak width. If the wavelength range is wide, near infrared light having a longer wavelength than visible light is more likely to cause chromatic aberration than visible light. Therefore, it is preferable to perform imaging in a wavelength range as narrow as possible.

The distribution of light transmittance as shown in fig. 6 can be obtained by the coating layer that a light transmittance peak of one third wavelength of the fundamental wave generated due to interference caused by the coating layer exists in the visible light peak wavelength region in the fundamental wave having a light transmittance peak in the near infrared light peak wavelength region. Preferably, the fundamental wave has a peak around 1550 nm. By forming the coating layer such that the light transmission peak of the fundamental wave of one half wavelength does not occur and the light transmission peak of one third wavelength becomes large, the light transmittance distribution satisfying the above condition can be obtained. It is possible to design and form a coating layer that gives a light transmittance distribution satisfying the above conditions by the prior art.

Fig. 8 shows an image using only near-infrared light, which is captured by the imaging lens 100 of embodiment 1, using the filter 54 having a small transmittance of visible light. An aircraft flying at a position at an estimated distance of 60km, which cannot be photographed under visible light, can be seen.

Fig. 9 shows an enlarged image of Tokyo sky tower (registered trademark) using only near infrared light, which is captured by the imaging lens 100 of embodiment 1. In contrast, fig. 10 shows an image captured with wavelengths of both visible light and near infrared light without using the filter 54 having a small transmittance of visible light. In fig. 10, since imaging is performed using wavelengths of both visible light and near infrared light having different focal lengths, an image is slightly blurred compared to fig. 9. Therefore, it is preferable to perform imaging by using only near infrared light or only visible light. Fig. 8 to 10 are each an image obtained by imaging a tokyo clear sky tower (registered trademark) from a point having a linear distance of about 30km by the imaging lens 100 of embodiment 1.

Example 2

Fig. 7 shows a light transmittance distribution of the imaging lens 100 according to embodiment 2. The light transmittance distribution shown in fig. 7 is corrugated in the visible light peak wavelength region VIS. On the other hand, no moire occurs in the NIR in the near infrared peak wavelength region. For example, waviness is easily generated in the case where the number of layers of the coating is small. That is, the number or size of the corrugations can be reduced by increasing the number of layers of the coating. Further, the number of ripples is the number of peaks. The size of the ripple is, for example, a height from a lowest position to a largest height among the adjacent peaks.

The NIR and/or VIS may also have corrugations in the near infrared peak wavelength region as shown in FIG. 7. Wherein the 1 st variable of at least one of the size and the number of the ripples representing the characteristic of the light transmittance fluctuation in the near infrared light peak wavelength region NIR may be smaller than the 2 nd variable of the corresponding size and the number of the ripples representing the characteristic of the light transmittance fluctuation in the visible light peak wavelength region VIS. Furthermore, the coating is preferably constructed in such a way that the NIR reduces the waviness in the near infrared peak wavelength region. By having a single transmittance peak without moire in the near infrared peak wavelength region NIR, the transmittance peak in the near infrared peak wavelength region NIR can be improved. This can improve the resolution of an image captured under near infrared light. Further, when the 1 st variable of the NIR of the near infrared light peak wavelength region to be compared is the size of the ripple, "the corresponding 2 nd variable in the size and number of the ripple in the visible light peak wavelength region" is the size of the ripple. And, when the 1 st variable of the NIR of the near infrared peak wavelength region compared is the number of waves, "the corresponding 2 nd variable of the size and the number of waves in the visible peak wavelength region" is the number of waves.

In the above embodiment, for example, as a hardware configuration of the control section 110, various processors or circuits shown below may be used. As described above, these include, in addition to a CPU that is a general-purpose processor that functions as each control unit by executing software (program), a PLD that can change a circuit configuration after the FPGA or the like is manufactured, a dedicated circuit having a circuit configuration specifically designed to execute a specific process such as an ASIC, a combination of a CPU and a PLD, an ASIC, or the like.

The control unit 110 may be configured by one of these various processors or circuits, or may be configured by a combination of two or more processors or circuits (for example, a combination of a plurality of FPGAs or a combination of a CPU and an FPGA) which are the same or different. Further, a plurality of control units may be configured by one processor.

As an example of a configuration of a plurality of control units by one processor, first, as represented by a computer such as a client and a server, there is a configuration in which one processor is configured by a combination of one or more CPUs and software, and the processor functions as a plurality of control units. Next, as represented by a System On Chip (SOC), a processor is used in which the overall function of the System including a plurality of control units is realized by one IC Chip. As described above, the control unit 110 can be configured using one or more of the above-described various processors as a hardware configuration.

As a hardware configuration of these various processors and circuits, more specifically, a circuit in which circuit elements such as semiconductor elements are combined can be used.

In the present specification, "a and/or B" is synonymous with "at least one of a and B". That is, "a and/or B" means that a alone, B alone, or a combination of a and B may be used. In the present specification, when three or more cases are expressed in "and/or" connection, the same point as "a and/or B" applies.

All documents, patent applications and technical standards described in this specification are incorporated by reference into this specification to the same extent as if each individual document, patent application or technical standard was specifically and individually indicated to be incorporated by reference.

Symbol description

1-imaging device, 10-objective lens, 12-focus lens, 14-zoom lens, 16-adjustment lens, 20-zoom lens driving mechanism, 22-turret driving mechanism, 24-adjustment lens driving mechanism, 26-image display portion, 28-input portion, 30-aperture, 50-filter switching portion, 52, 54, 56, 58-filter, 90-frame, 100-imaging lens, 110-control portion, 112-bus, 114-zoom lens driving portion, 116-turret driving portion, 118-adjustment lens driving portion, 120-output I/F, 122-input I/F, 126-image processing portion, 130-imaging portion, 132-imaging element, 132A-imaging surface, 200-computer, 202-CPU,204-RAM,206-ROM, 210-imaging device control program, 212-focus position data.

Claims

1. An imaging lens having a plurality of lenses,

by applying a coating to at least a part of the plurality of lenses, in a near-infrared light wavelength region, light transmittance from a short wavelength end of the near-infrared light peak wavelength region at a wavelength shorter than a near-infrared light peak wavelength region including 1550nm decreases with a shorter wavelength, and light transmittance from a long wavelength end of the near-infrared light peak wavelength region at a wavelength longer than the near-infrared light peak wavelength region decreases with a longer wavelength,

the light transmittance in the near infrared peak wavelength region is 60% or more,

by applying the coating layer to at least a part of the plurality of lenses, in a visible light wavelength region, a transmittance of a wavelength side shorter than a visible light peak wavelength region including a range of 500nm to 650nm decreases as a wavelength becomes shorter from a short wavelength end of the visible light peak wavelength region, and a transmittance of a wavelength side longer than the visible light peak wavelength region decreases as a wavelength becomes longer from a long wavelength end of the visible light peak wavelength region,

the transmittance of a wavelength region on the short wavelength side in a blue wavelength region included in the visible wavelength region is lower than the transmittance of a wavelength region on the long wavelength side in the blue wavelength region,

The 1 st variable representing at least one of the size and the number of the ripples of the light transmittance fluctuation characteristic in the near infrared light peak wavelength region is smaller than the corresponding 2 nd variable representing the size and the number of the ripples of the light transmittance fluctuation characteristic in the visible light peak wavelength region.

2. The imaging lens as claimed in claim 1, wherein,

the wavelength region on the short wavelength side of the blue wavelength region is a wavelength region of 450nm or less.

3. The imaging lens as claimed in claim 1, wherein,

the light transmittance at 400nm to 430nm is 50% or less.

4. The imaging lens as claimed in claim 1, wherein,

by applying the coating to at least a part of the plurality of lenses, there is a low light transmittance region having a light transmittance smaller than the near infrared light peak wavelength region and the visible light peak wavelength region between the near infrared light peak wavelength region and the visible light peak wavelength region.

5. The imaging lens as claimed in claim 4, wherein,

the low light transmittance region is a wavelength region of 900nm to 1100nm, and the light transmittance in the wavelength region of 900nm to 1100nm is 5% or less.

6. The imaging lens as claimed in claim 1, wherein,

A light transmittance peak of one third wavelength of a fundamental wave generated due to interference caused by the coating layer in the fundamental wave having a light transmittance peak in the near infrared light peak wavelength region exists in the visible light peak wavelength region.

7. The imaging lens as claimed in any one of claims 1 to 6, wherein,

the imaging lens includes a filter switching section,

the filter switching unit can dispose at least one of a 1 st filter that reduces the transmittance of at least a part of visible light and a 2 nd filter that reduces the transmittance of at least a part of near infrared light on an optical path.

8. The imaging lens as claimed in claim 7, wherein,

the product of the refractive index and the thickness of the 2 nd filter is greater than the product of the refractive index and the thickness of the 1 st filter.

9. The imaging lens as claimed in claim 7, comprising the filter switching section,

the filter switching section is disposed closer to the imaging side than a lens located closest to the imaging side among the plurality of lenses.

10. The imaging lens as claimed in claim 7, wherein,

the imaging lens includes a control section that,

the control unit has focus position information indicating a focus position when the 1 st filter or the 2 nd filter is disposed on the optical path, and performs control to change a position of the focus position adjustment lens when the 1 st filter is disposed on the optical path and when the 2 nd filter is disposed on the optical path based on the focus position information.

11. The imaging lens according to any one of claims 1 to 6, comprising a zoom optical system.

12. An imaging apparatus, comprising:

the imaging lens of any one of claims 1 to 11; and

and an InGaAs imaging element for imaging the object through the imaging lens.